Different Image Problem for 2.5 (1 post)

I've been looking at the problems other people have had with uploading images on the new 2.5 upgrade but I haven't seen this error yet. When I try to upload images or get/view the images that are already on the server I get this message:

"Fatal error: Call to undefined function: image_downsize() in /var/www/vhosts/midnightlights.com/httpdocs/wp-includes/post.php on line 2326"